The aim was to study the roles that the bone marrow mesenchymal stem cells (MSC) and cytokines play in cord blood CD34(+) cell expansion ex vivo and the influence of culture ex vivo on expression of the adhesive molecule of CD44. CD34(+) cells sorted from cord blood cells had been cultured in each well of 24 well culture plates containing culture medium supplemented with mesenchymal stem cells layer or/and cytokines for a week, and then all kinds of indexes of different groups were compared. The results showed that as for cord blood cell expansion, there was no significant difference between the groups with cytokines SDF-1alpha + SCF + TPO + FL and SCF + TPO + FL no matter if MSC layer existed or not. The groups with MSC layer and cytokines were superior to the corresponding groups without MSC layer. In addition, the expression of the adhesion molecule CD44 had no distinct change after culture. It is concluded that SDF-1alpha has no distinct influence on the effect of cytokines SCF + TPO + FL on cord blood cell expansion ex vivo. MSC enhance the effect of cytokines on cord blood cell expansion ex vivo. Such expansion ex vivo may not influence the expression of the adhesive molecule CD44 on cord blood cells.